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Abstract:

An eolic turbine is disclosed, comprising: a hub (1) revolvingly mounted
on a tower, around a basically horizontal axis, and provided with a slow
speed shaft that drives into rotation a rotor of an electric generator, a
plurality of blades (P) radially protruding from the hub (1) and
revolvingly mounted around their axis, and an adjusting device of the
blade pitch to adjust the angle of rotation of each blade around its
axis. The adjusting device of the blade pitch comprises a geared motor
(6) comprising a rotary case (60) fixed to a mobile plate (5) joined to
the blade (P), and a fixed case (61) fixed to a fixed plate (7) joined to
the hub (1).

Claims:

1) Eolic turbine comprising:a hub (1) revolvingly mounted on a tower,
around a basically horizontal axis, and provided with a slow speed shaft
that drives into rotation a rotor of an electric generator,a plurality of
blades (P) radially protruding from the hub (1) and revolvingly mounted
around their axis, andan adjusting device of the blade pitch to adjust
the angle of rotation of each blade around its axis;characterized in
thatthe adjusting device of the blade pitch comprises a geared motor (6)
comprising:a rotary case (60) of the output stage of the reduction gear
fixed to a mobile plate (5) joined to the blade (P) to allow for rotation
of the blade (P) around its axis, anda fixed case (61) of the motor of
the geared motor (6) fixed to a fixed plate (7) joined to the hub (1).

2) Eolic turbine as claimed in claim 1, characterized in that it comprises
a bearing (8) comprising an internal ring (81) fixed to the mobile plate
(5) and an external ring (80) fixed to the hub (1).

3) Eolic turbine as claimed in claim 1, characterized in that the geared
motor (6) comprises an electric motor and an epicyclical reduction gear
with multiple stages, in which the rotary case (60) of the output stage
of the reduction gear is fixed to the mobile plate (5).

4) Eolic turbine as claimed in claim 1, characterized in that the geared
motor (6) is arranged axially with respect to the mobile plate (5).

5) Eolic turbine as claimed in claim 2 characterized in that the mobile
plate (5) comprises a peripheral ring (50) connected to a central flange
(52) by means of a plurality of spokes (51), in which the peripheral ring
(50) of the mobile plate is fixed to the internal ring (81) of the
bearing and the central flange (52) of the mobile plate is fixed to the
rotary case (60) of the output stage of the geared motor (6).

6) Eolic turbine as claimed in claim 1, characterized in that the fixed
plate (7) comprises a central flange (72) fixed to the fixed case (61) of
the motor of the geared motor and at least two radial spokes (70) that
branch off from the central flange (72) ending in corresponding
peripheral portions (70) fixed to the said hub.

Description:

[0001]The present patent application for industrial invention relates to
an eolic turbine, and in particular to an adjusting device of the blade
pitch.

[0002]As it is known, an eolic turbine comprises a hub revolvingly mounted
on a nacelle supported by a tower. A plurality of blades is radially
mounted on the hub to exploit the thrust of the wind. The assembly of hub
and blades is the aerodynamic rotor. A shaft, defined as slow speed
shaft, is joined to the hub and connected to a rotor of an electrical
generator for production of electricity.

[0003]Obviously, the speed of the wind changes continuously in an
unpredictable uncontrollable way. When the speed of the wind increases,
also the supplied power increases and consequently, the loads on the
turbine increase according to the increment of the speed of the wind
squared. To avoid damage, without having to design the turbine for any
speed of the wind (since it would be uneconomic) it is necessary to limit
the power and design the turbine according to said limit. The systems
that are commonly used to limit power in turbines with horizontal axis
(i.e. the most popular systems) are: [0004]controlling the variation of
the blade pitch, and [0005]controlling the (active or passive) stall of
the blades.

[0006]Leaving aside the case of passive stall control, for which the blade
does not rotate entirely, the other two cases will be considered, in
which the blades are rotated around their longitudinal axis by hydraulic
or electromechanical actuators.

[0007]The rotation of the blades induces a variation of the incidence
angles with respect to the air current and therefore a variation of the
aerodynamic characteristics of the aerodynamic rotor (being said
characteristics related to the forces).

[0008]Pitch Variation Control

[0009]In this case, a sensor reads the electrical power supplied by the
generator and when it exceeds the nominal value, the electronics imposes
an increase of the pitch that reduces the power, bringing it back below
the nominal value. On the contrary, when the wind goes down and power
drops below the nominal value, the electronics imposes a reduction of the
pitch.

[0010]In a situation with high turbulent wind, the actuation devices are
particularly stressed.

[0011]Active Stall Control

[0012]In this case the control of the electrical power of the generator
occurs, when the speed of the wind increases, by exceeding the stall
incidence angle beyond which a considerable reduction of the aerodynamic
characteristics of the hub is obtained.

[0013]The conditions in which stall occurs can be changed by changing the
coupling of the blade with respect to the hub. This is obtained by means
of hydraulic or electromechanical mechanisms, such as in the case of
pitch variation control.

[0014]In case of active stall control, variations are much slower than
pitch variation control, but the actuation system is subject to
considerable stress because it represents a constraint to the torsion of
the blade.

[0015]FIG. 1 is a diagrammatic view of a hub according to the prior art,
which is generally indicated with numeral (1). The hub (1) comprises a
plurality of circular housings (10) (three housings are illustrated in
the figure) for fixing the blades and a circular flange (3) for fixing
the slow speed shaft.

[0016]A bearing (2) is disposed in each housing (10). The external ring
(20) of the bearing (2) is fixed to the housing of the hub (1); whereas
the internal ring (21) of the bearing is fixed to the attachment of the
blade. The internal ring (21) of the bearing is provided with internal
toothing (22) in such a way to generate a thrust block or tooth wheel
(21).

[0017]An electrical motor (4) is jointly disposed inside the hub (1) to
rotate a pinion (42) that engages on the internal toothing (22) of the
internal ring (21) of the bearing. A reduction gear (41), such an
epicyclical reducer with multiple stages, is interposed between
electrical motor (4) and pinion (42).

[0018]During the normal operation of the hub (1) cyclic forces are
developed, which tend to open and close, at every revolution of the hub
(1), the pinion (42)--toothed wheel (21) coupling.

[0019]Therefore, high wear and localized corrosion (pitting) of the
toothing that work along an arch of about 90° are generated. In
the attempt to limit such a drawback, the toothing of pinion (42) and
toothed wheel (21) must be suitably dimensioned, in such a way they can
adequately withstand the fatigue stress.

[0020]In any case, expensive maintenance works are necessary on the
toothed wheel, because of the fact that, by working along an arch of
90°, after a certain number of operation cycles, it wears out and
must be rotated to engage another wear-free arch of 90°. Such a
repositioning implies the disassembly of the blade that is made with
expensive external cranes.

[0021]Moreover, it must be considered that the pinion (42)--toothed wheel
(21) coupling needs grease lubrication that does not favor ideal working
conditions.

[0022]The purpose of the present invention is to eliminate the drawbacks
of the prior art, by disclosing an eolic turbine provided with adjusting
device of the blade pitch that is efficient, efficacious, versatile and
reliable.

[0023]Another purpose of the present invention is to provide such an eolic
turbine provided with adjusting device of the blade pitch that is
inexpensive and easy to install and maintain.

[0024]These purposes are achieved by the present invention, the features
of which are claimed in the independent claim 1.

[0025]Advantageous embodiments are disclosed in the dependent claims.

[0026]The eolic turbine of the invention provides for an adjusting system
of the blade pitch, in which the pinion-toothed wheel coupling is
eliminated, connecting the output rotary case of the reduction gear
directly with the ring of the bearing joined with the blade.

[0027]To do so, two plates are necessary: a plate joined with the hub
(fixed part with respect to the blade) to which the fixed case of the
motor is connected, and a plate joined with the blade to which the rotary
case of the geared motor is connected.

[0028]The following advantages are obtained with the proposed solution:
[0029]general cost reduction; as a matter of fact, the elimination of
pinion and toothing on the ring of the bearing of the blade largely makes
up for the addition of the plates and of an additional epicyclical stage
in the geared motor. [0030]Optimized working conditions of gears that
work in oil bath being closed in the case of the reduction gear.
[0031]Elimination of pitting problems on toothing. [0032]Elimination of
expensive maintenance works on the toothed wheel.

[0033]Additional characteristics of the invention will become evident from
the detailed description below, which refers to a merely illustrative,
not limiting, embodiment, as shown in the enclosed figures, wherein:

[0034]FIG. 1 is a diagrammatic perspective view of a hub of an eolic
turbine according to the prior art, in which the adjusting system of the
blade pitch is shown;

[0035]FIG. 2 is a diagrammatic perspective view of a hub of an eolic
turbine according to the invention;

[0036]FIG. 3 is a cutaway view of the hub of FIG. 2, in which the
adjusting system of the blade pitch is shown.

[0037]In the following text identical elements or elements that correspond
to elements that have already been described are indicated with the same
reference numerals, omitting their detailed description.

[0038]FIGS. 2 and 3 show a hub (1) with two blades (P) illustrated as
interrupted.

[0039]According to the invention each blade (P) is joined to a mobile
plate (5). The mobile plate (5) comprises a peripheral ring (50)
connected by means of radial spokes (51) to a central flange (52).

[0040]The mobile plate (5) is revolvingly mounted in the corresponding
circular housing of the hub (1) by means of a ball or roll bearing (8).
In view of the above, the external ring (80) of the bearing (8) is joined
to the hub (1); whereas the internal ring (81) of the bearing is joined
to the peripheral part (50) of the mobile plate (5). Balls or rolls (82)
are disposed between the external ring (80) and the internal ring (81).

[0041]The central flange (52) of the mobile plate is fixed to a rotary
case (60) of a geared motor (6) that represents the outgoing stage of the
geared motor. The geared motor (6) is disposed in axial position with
respect to the to mobile plate (5).

[0042]The geared motor (6) comprises an electrical motor and a reduction
gear, composed for example of multiple stages of epicyclical reducers, in
which the rotary case (60) of the outlet stage of the reducer is
connected to the central flange (52) of the mobile plate (5).

[0043]The electrical motor of the geared motor (6) provides for a fixed
case (61) that is fixed to the hub (1) by means of a fixed plate (7). The
fixed plate (7) is provided with a central flange (72) from which at
least two spokes (71) ending with a peripheral flange (70) branch off
radially. Preferably, the fixed plate is provided with two spokes (70)
arranged in diametrically opposite positions.

[0044]The central flange (72) of the fixed plate is fixed to the fixed
case (61) of the motor of the geared motor; whereas the peripheral flange
(70) of the fixed plate is fixed to the hub (1).

[0045]Numerous variations and modifications can be made to the present
embodiment of the invention by an expert of the art, while still falling
within the scope of the invention as claimed in the enclosed claims.

Patent applications in class Including pitch lock or adjustable stop

Patent applications in all subclasses Including pitch lock or adjustable stop